Five critical vulnerabilities found in Cisco Discovery Protocol (CDP) could allow attackers to take over tens of millions of enterprise devices as discovered by IoT security company Armis. CDP is a proprietary Layer 2 (Data Link Layer) network protocol used by Cisco devices for discovering info on other Cisco equipment on the local network. More than 95% of all Fortune 500 companies and over 200,000 customers use Cisco Collaboration solutions according to Cisco’s stats. Many vulnerable devices also do not provide users with the ability to turn CDP off as a workaround.
Source: https://www.bleepingcomputer.com/news/security/cisco-patches-critical-cdp-flaws-affecting-millions-of-devices/